Process for frothing rubber latex



Patented Nov. 11 1952 PROCESS FOR FROTHING RUBBER LATEX Charles F. Eckert, Westwood, N. J assignor to United :States Rubber Company, New York, N. Y., a corporation of New Jersey No Drawing. Application June 10, 1950,

Serial No. 167,494 1 8 Claims.- (01. 260-723) heating, by the addition of known gelling agents,

such as alkali-metal silicofluorides, orit maybe coagulated by freezing, with or. without the addition of a coagulant, in known manner. The general procedure followed in the preparation of latex sponge by hydrogen peroxide decomposition is to thoroughly intermix in a latex the usual compounding ingredients, such as-curatives, accelerators, and antioxidants, and add to this mixture the hydrogen peroxide and catalyst for its decomposition. It is essential, in order to insure even blowing of the sponge, that the hydrogen peroxide and catalyst be thoroughly intermixed in the latex. This is, however, very diflicult to do because invariably when the hydrogen peroxide and catalyst come into contact in the latex, the hydrogen peroxide commences to decompose very rapidly, frothing the latex to such a degree that further intermixing of the hydrogen peroxide and catalyst in the latex, in order to insure a uniform, porous structure upon completion of blowing, is impossible because of the great increase in volume and viscosity of the latex. In addition, due to this rapid initial frothing, it is frequently impossible to carry out the often desirable operating procedure of pouring the latex into a mold, so that in frothing it will take the shape of the mold. In order to obtain a homogeneous dispersion of the blowing agent and catalyst in the latex with conventional mixing apparatus, one-half minute to one minute of mixing is'necessary. For most purposes an additional half minute to a minute, after intermixing is complete but beforerapid frothingoccurs, is desirable so that the slowly frothing latex may be poured into a mold. This rapid initial decomposition of the hydrogen peroxide is especially evident when catalysts such as the various catalases, e. g., those found in yeast, beef or other animal liver, are used to speed up the decomposi tion of the hydrogen peroxide. 1 I

. The object of the present invention is to slow down the initial rate of decomposition of hydrogen peroxide with catalase decomposition catalyst in latex in the manufacture of sponge rubber without appreciably reducing the amount of oxygen evolved or the blowing that takes .place in the sponge, as measured by the total volume increase in the latex on foaming.

According to the present invention, latex is foamed by the catalase catalyzed decomposition of hydrogen peroxide in the presence of a small amount of hydroxylamine which acts as a catalyst retarder and slows down the initial decomposition rate of the hydrogen peroxide. 2

In carrying out the present invention, the hydrogen peroxide, catalase and hydroxylamine may be added to a latex which is at room temperature or to a latex that has'been' cooled to 0 to 15 (3., which cooling still further slows down theinitial decomposition rate of the hydrogen peroxide. The hydroxylamine is preferably added to the latex in an aqueous medium similarly to the hydrogen peroxide and catalase, and

' preferably is in the form of a salt, such as hydroxylamine hydrochloride or hydroxylamine sulfate. The aqueous hydroxylamine may be added to the latex, or may be intermixed with the catalase and then'added tothe latex. It is only important not to bring the hydrogen peroxide and catalase together in the latex unless the 'hydroxylamineis present.

The amount of hydrogen peroxide for decomposition of the latex isthat conventionally used for frothing latex, viz., 1- to '7 partsby weight of hydrogen peroxide (H202) per parts of rubber of the latex depending onthe density desired in the final product. The amount of catala se to give satisfactory activation of the hydrogen pe roxide will be a catalytic 'amountas commonly used for the purpose, generally from 5 to 20 percent of the weight of the hydrogen peroxide (H202) The amount of hydroxylamineto be used depends on the rate of hydrogen peroxide decomposition desired, and on the nature "of the catalase, which may be obtained from yeast or from the liver of various animals Large amounts of hydroxylamine poison the catalases, and lesser amounts will cause too slow a decomposition reaction. The amount of hydroxylamine will be a catalyst retarding amount, and preferably should be only such amount as to give the maximum rate of blowing that can be tolerated in the particular foaming and molding operation under consideration. The amount of hydroxylamine generally will be less than 1% of the weight of the catalase, and may be as low as 0.0l.%.by weight of the catalase... 11 .i u

The following examplesare'illustrativer of the 3 invention, all parts and percentages referred to therein being by weight:

Example I An ammonia preserved natural rubber (once creamed) latex of 68% solids concentration was deammoniated by' blowing air therethrough, and was compounded according "-to the following formulation, compounding ingredients being added as conventional aqueous solutions and pastes:

z. Par-ts byweight Dry Wot Basis Basis Latex 147 20% aqueous potassium oleate 1 5 Curing paste:

Sulfur 2. 5

5. Zinc diethyldit'hiocarbamate 0.65 .Zincsaltpf 2 mercaptobenzothiazole. 1.25 D isper'sing agents i i 2 Water. 6L4 Antioxidant paste" Antioxidant" 0.5 Dispersing agent 0. 42 1 Water 0.48

To a portio -of the ratexza 0- :t er w added w th st rrin erve t-of catala e-i e "aqu ousisus ens on, and 1 Parts f hyd o en peroxide .(HzQg) 1- in a-;;30% ,iaqueous solution-per .00 parts of rubbe of-the lat x'e mpoun The same-amounts of .catalas zan hydr n p xi were laddeditoa ;s econd-p'ortion but in this -.case

0.000135-partofjhydroxylamine (per 100 parts-of rubber) as a .0.007% aqueous solution of "hy- ,droxylamine hydrochloride was added after the catalase .and'1before1the hydrogen peroxide. The same amounts of catalase-and- -hydrogen peroxide were -added-to a.f-11hi1fd portion but ;in this 0ase:0.00Q3-1 part of hydroxylamine (per' IOOparts .-.of-rubber)" a s a:0.007"% aqueous solution of hyd,roxylamine hydrochloride was added after. the zcatalase and before the :hrdmeen x q *T e time whi h relaps d after th h dro p r ide-zadditionefore 1 1 no hi lat x attained za'wolum oftwice the orieinali iqu d 'le e 4 seconds in the first portion 'l-asecondsin the sec- 0nd portion, and ;34 seconds in ithei-third portion. "The time which-elapsedbefore -;the*--volume of froth was three times the original latex volume was 8-secondstin the f rst portion,;23 s econds in the ssecond :portion; and 167 seconds ;in the third portion. :Th tim whi ap d o the volumeof' frothwas five; times the-original latex volume was 1-8 seconds ginthe first portion, 60 secondsini the-second -portion,q and 11 0 7 seconds zinithethird portion. The-timewhichelapsed before, the omm of re hwa i times t einalclatexyo umerwas fies n si h firstpo ,tion, 117.- seconds the second portion, and 188 seconds in t e-1thind '-po t ,It. is evident from1 these I results that by "the inclusion of hydroxylamine, the initial decomposition-of the hydr n p oxid is :mad

.proceethat asufilciently slower .raect ive equate time for -(the: necessary manipulative operations before-completion of the blowing.

Example 11 The latex used was the same as "Example I. In thisxcase the-latex was cooledtow5 C. To -one portion of the cooled1latex waswadded the same 0.34 part of catalaseeandquparts of hydrogen-peroxide eas d-n Example :I. a second 4 portion of the cooled latex was added these same amounts of catalase and hydrogen peroxide but with the addition of 0.000135 part of hydroxylamine similarly to the second portion in Example 1-92 seconds in the second portion. The time which elapsed'before the volume of froth was eight times the original latex volume was 98 seconds-inthe first portion, and 249 seconds in the second portion.

The hydroxylamine reduced the initial decomposition rate of the hydrogen peroxide in the cooled latex as shown :in the above. Comparing the above'results with" those in .the first example,

it isseenthat'the coolingialone results in a slower initial decomposition-rate butthat the in creased delay achieved with the hydroxylamine where 0.00031 parts was added in Example I, is longer' than i that resulting from the cooling alonegas in the'first portion in Example-II.

Example III 'An ammonia',preserved'natural rubber ,(once centrifuged, twice creamed) latex.of 58.2% solids concentration wasld'eammoniated by blowing air therethrough, and additionallystabilized with .20 .parts (wet) of 10% aqueous. solution of dimethylaminecaseinate :per -100 parts ofsolids ofthe latex. The 'latexwas compounded according to the following formulation, the compounding ingredients being added as :aqueous solutions -or pastes:

Parts by weight Dry 7 Basis Basis Latex 20% aqueous stabilizer solution (reaction product'of ethylene oxide and isopropyl phenol) 1 5 Curmg. paste:

Sulfur Zinc oxide gZinc diethyl dithiocarbama'te.

Zincsalt of 2emercaptobe t Dispersing agents. Water:

Antioxidant paste:

Antioxidant; Dis'persingagenL Forty ml. (millili-tres) of ;30% hydrogen peroxide-were then" 512ilredqinto-816 grams .(four formula weights) of theaabove compoundedlatex. Whenthe hydrogen-peroxide was evenlydispersed throughout the latex, "40 ml. of a 2% aqueous catalasesolution andgldml. of a 0.0039'.%:=aqueous solution of {hydroxylamine hydrochloride were intermixed and addedto :the latex with-vigorous stirring. Stirring was-contin'ued .for about: one

minute; during this period ithe latex :slowly frothed to double its-original volume. It was 'then poured intoamold. "Frothing became rapid almost immediately-afterspouring. After. frothing was complete the/porous flatex' was coagulated? by freezing at .i60 1C. for 45 minutes. The coagulated ;1atex-was thien cured by: placing it underatmsp eric steam :io pne-hau ho The resultant cured sponge had a, density of .157 g./cc., and a good structure. I

The latex for preparing sponge rubber according to the present invention may be a natural rublatex, or mixtures of any of the same. Such conjugated diolefine polymer synthetic rubber latex may be an aqueous emulsion polymerizate of one or a mixture of butadienes-1,3, for example, butadiene-1,3, 2-methyl-butadiene-L3' (isoprene), 2 chloro-butadiene-1,3 (chloroprene), piperylene,2,3-dimethyl-butadiene-1,3. The conjugated diolefine polymer synthetic rubber latex, as known, may be made from a mixture of one or more of such butadienes-1,3 with one or more other polymerizable compounds which are capable of forming rubbery copolymers with butadienes- 1,3, for example, up to 70% of such mixture of one or more compounds which contain a. single CH2=C group where at least one of the disconnected valences is attached to an electronegative group, that is, a group which substantially increases the electrical dissymmetry or polar character of the molecule. Examples of compounds which contain a CH2=C group and.

are copolymerizable with butadienes-1,3 are aryl olefines, such as styrene, and vinyl naphthalene; the alpha-methylene carboxylic acids, and their esters, nitriles and amides, such as acrylic acid, methyl acrylate, methyl methacrylate, acryl-' onitrile, methacrylonitrile, methacrylamide;

' methyl vinyl ether; methyl vinyl ketone; vinylidene chloride.

In view of the many changes and modifications that may be made without departing from the principles underlying the invention, reference should be made to the appended claims for an understanding of the scope of the invention.

Having thus described my invention what I claim and desire to protect by Letters Patent is:

l. The process of frothing latex selected from the group consisting of ammonia preserved natural rubber latex and conjugated diolefine polymer synthetic rubber latex by the evolution of oxygen in the latex which comprises incorporating in the latex at a temperature between C. and 30 C, hydrogen peroxide and catalase decomposition catalyst for the hydrogen peroxide, and hydroxylamine in small quantity efiective to retard the catalyst activity of the catalase and to slow down the initial rate of the hydrogen peroxide decomposition.

2. The process of frothing latex selected from the group consisting of ammonia preserved natural rubber latex and conjugated diolefine polymer synthetic rubber latex by the evolution of oxygen in the latex which comprises incorporating in the latex at a temperature between 0 C. and 15 C. hydrogen peroxide and catalase decomposition catalyst for the hydrogen peroxide, and hydroxylamine in small quantity effective to retard the catalyst activity of the catalase and to slow down the initial rate of the hydrogen peroxide decomposition.

3. The process of frothing ammonia preserved natural rubber latex by the evolution of oxygen in the latex which comprises incorporating in the latex at a temperature between 0 C. and 30 C. hydrogen peroxide and catalase decomposition catalyst for the hydrogen peroxide, and hydroxylamine in small quantity effective to retard the catalyst activity of the catalase and to slow down her latex, as in the illustrative examples above, or a,cor'ijugated diolefine polymer synthetic rubber peroxide, decom- ,natural'rubber. latex by the evolution of oxy en in the latex which comprises incorporating, in the latex at a temperature between 0 C. and 15 C. hydrogen peroxide and catalase decomposition catalyst for the hydrogen peroxide, and hydroxylamine in small quantity effective to retard the catalyst activity of the catalaseand to slow down the initial rate of theh'ydr'ogen' peroxide decomposition.

5. The process of frothing latex selected from the group consisting of ammonia preserved natural rubber latex and conjugated diolefine polymer synthetic rubber latex by the evolution of oxygen in the latex which comprises incorporating in the latex at a temperature between 0 C. and 30 C. hydrogen peroxide and catalase decomposition catalyst for the hydrogen peroxide, and hydroxylamine in small quantity efiectlve to retard the catalyst activity of the catalase and to slow down the initial rate of the hydrogen peroxide decomposition, the amount of hydrogen peroxide being 1 to 7 parts by weight per parts of rubber of the latex, the amount of catalase being 5 to 20 percent of the weight of the hydrogen peroxide, and the amount of hydroxylamine being 0.01 to 1 percent of the weight of the catalase.

6. The process of frothing latex selected from the group consisting of ammonia preserved natural rubber latex and conjugated diolefine polymer synthetic rubber latex by the evolution of oxygen in the latex which comprises incorporating in the latex at a temperature between 0 C. and 15 C. hydrogen peroxide and catalase decomposition catalyst for the hydrogen peroxide, and hydroxylamine in small quantity efiective to retard the catalyst activity of the catalase and to slow down the initial rate of the hydrogen peroxide decomposition, the amount of hydrogen peroxide being 1 to 7 parts by weight per 100 parts of rubber of the latex, the amount of catalase being 5 to 20 percent of the weight of the hydrogen peroxide, and the amount of hydroxylamine being 0.01 to 1 percent of the weight of the catalase.

7. The process of frothing ammonia preserved natural rubber latex by the evolution of oxygen in the latex which comprises incorporating in the latex at a temperature between 0 C. and 30 C. hydrogen peroxide and catalase decomposition catalyst for the hydrogen peroxide, and hydroxylamine in small quantity effective to retard the catalyst activity of the catalase and to slow down the initial rate of the hydrogen peroxide decomposition, the amount of hydrogen peroxide being 1 to 7 parts by Weight per 100 parts of rubber of the latex, the amount of catalase be ing 5 to 20 percent of the weight of the hydrogen peroxide, and the amount of hydroxylamine being 0.01 to 1 percent of the weight of the catalase.

8. The process of frothing ammonia preserved natural rubber latex by the evolution of oxygen in the latex which comprises incorporating in the latex at a temperature between 0 C. and 15 C. hydrogen peroxide and catalase decomposition catalyst for the hydrogen peroxide, and hydroxylamine in small quantity effective to retard the catalyst activity of the catalase and to slow down the initial rate of the hydrogen peroxide decomposition, the amount of hydrogen peroxide being 1 to 7 parts by weight per 100 parts 0! rubber 0f the latex, the amount of catalase being 5 to 20 percent of the weight of the o'f the hydrogen peroxide, and-the amount cf' hydroxyl- -=a.mine being 0.01 to 1 percent of the weight of the'cztal'ase.

CHARLES F. ECKERT.

"file" of "this" patent:

- s UNITED STATES PATENTS Number 12126268 2,138,081 214321353 2,540,040

Date

Name McGava'ck Aug. 1938 "Wolf Nov."29, 1938 Tammy V Dec. 9,1947 Baker 7 'Jan.'-30,'1951 

1. THE PROCESS OF FROTHING LATEX SELECTED FROM THE GROUP CONSISTING OF AMMONIA PRESERVED NATURAL RUBBER LATEX AND CONJUGATED DIOLEFINE POLYMER SYNTHETIC RUBBER LATEX BY THE EVOLUTION OF OXYGEN IN THE LATEX WHICH COMPRISES INCORPORATING IN THE LATEX AT A TEMPERATURE BETWEEN 0* C. AND 30* C. HYDROGEN PEROXIDE AND CATALASE DECOMPOSITION CATALYST FOR THE HYDROGEN PEROXIDE, AND HYDROXYLAMINE IN SMALL QUANTITY EFFECTIVE TO RETARD THE CATALYST ACTIVITY OF THE CATALASE AND TO SLOW DOWN THE INITIAL RATE OF THE HYDROGEN PEROXIDE DECOMPOSITION. 